Re: [dpdk-dev] [PATCH] examples/l3fwd: prefetch the content of the next packet

[Thomas Monjalon <thomas@monjalon.net>]

+Cc Konstantin

14/08/2019 10:54, Feifei Wang:
> The cache-misses problem is very serious when the function
> lpm_cb_parse_ptype is called to read the content of packets. That is
> because the contents of packages previously stored in the cache are
> overwritten by the following instructions or variables.
> Thus the prefetch order can be used to prefetch the next packet into
> the cache to avoid CPU spending too much time on it.
> 
> On Octeon TX platform with built-in NIC, 12% performance gain was
> measured by running RFC2544 NDR test with l3fwd. Furthermore, the
> cache-misses event of the function lpm_cb_parse_ptype was reduced by
> 20%, and the CPU task-clock of it dropped from 16.49% to 11.3%, based
> on the forwarding test for one minute with the 64B packet.
> On the dpaa2 platform, no performance improvement nor drop were seen
> with this patch by running RFC2544 NDR test with l3fwd.
> On the x86 platform, 15.7% performance gain was measured by running
> RFC2544 NDR test with l3fwd.
> 
> Signed-off-by: Feifei Wang <feifei.wang@arm.com>
> Reviewed-by: Gavin Hu <gavin.hu@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> Reviewed-by: Phil Yang <phil.yang@arm.com>

Let's test this "improvement" with 19.11-rc1.
If a drawback is seen, the patch can be reverted.

Applied, thanks